EPIPHYTIC DIATOMS IN FARM PONDS AND EXPERIMENTAL PONDS IN BRYAN COUNTY, OKLAHOMA

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1 64 EPIPHYTIC DIATOMS IN FARM PONDS AND EXPERIMENTAL PONDS IN BRYAN COUNTY, OKLAHOMA William W. Troeger USDA Water Quality Management Laboratory, Durant, Oklahoma Submersed macrophytes Najas quadalupensis and Chara sp. in four Bryan County, Oklahoma ponds supported diverse populations of epiphytic diatoms. A total of 25 genera and 130 taxa were present in 40 samples taken in May and in August The genus Navicula had the most species followed by Nitzschia and Pinnularia. Achnanthes linearis and Cocconeis placentula were the most abundant taxa. Fifty-seven new taxa were found for Oklahoma. INTRODUCTION Until recently, few articles have been published on diatoms in Oklahoma. Maloney (1) and Leake (2) reported diatoms in a stream and small lakes in central Oklahoma. Koch and Risser (3) studied algal communities on leaf detritus in a stream, and Koch (4) reported on diatoms in southwestern Oklahoma. Pfiester and Terry (5) provided recent observations of newly identified Oklahoma algae. Cooper and Wilhm (6) included diatoms in their study of effects of industrial effluents on a stream. Other Oklahoma diatoms were reported by Wilhm et al. (7) and Seyfer and Wilhm (8). This paper reports on the relative proportions of diatoms epiphytic on submersed macrophytes in four ponds in Bryan County, Oklahoma. MATERIALS AND METHODS Pond Description. Two farm ponds and two model ponds were studied (Table 1). The two farm ponds (1A and 15), located in Bryan County near Durant, Oklahoma, were used primarily for livestock watering and fish raising. Both were over 10 years old and had a broad development of macrophytes including cattails, sedges, and rushes as well as mats of macrophytes growing on the pond bottoms. Chara sp. was the predominant bottom macrophyte in 1A while Najas guadalupensis (Spreng). Morong was abundant in 15. Watersheds for ponds 15 and 1A contained San Saba clay and Bowie loam soils, respectively. Model ponds (8 and 9) were located at the Water Quality Management Laboratory (WQML) in Durant, Oklahoma, and were established in 1974 to study phosphorus enrichment. These ponds had much smaller surface areas and volumes than the farm ponds and were contained in glass-coated steel silo sections. Pond rims were 0.2 m above the ground, thereby preventing inflow. Pond 8 contained San Saba sediment from the farm pond 15 watershed and pond 9 had Bowie soil from farm pond 1A watershed. Each received mud and water inoculum from its respective watershed pond when they were first built in Both model ponds contained large benthic stands of Najas guadalupensis, which were harvested periodically. Sample Gathering and Processing Five macrophyte samples for diatom analysis were taken twice from each of the four ponds; this produced 40 samples. Farm ponds were sampled on 5/19/76 and Proc. Okla. Acad. Sci. 58: (1978)

2 65 8/3/76; model ponds were sampled on 5/20/76 and 8/4/76. Samples were taken near the pond bottom about m below the water surface. In the farm ponds two locations were near the dam and the other three were away from the dam. In the model ponds four locations were distributed around the pond about 1 m from the walls and the fifth location was in the center. Samples consisted of macrophytes lifted from the bottom and placed in plastic whirlpacks. Chara sp. was used in pond 1A, whereas Najas guadalupensis was used in the other three ponds. On the sampling day whole macrophytes totaling about 4 m in length per sample were placed in a solution of hydrogen peroxide and potassium dichromate to remove organic matter from the diatom frustules, as well as to remove diatoms from the macrophytes (9). Diatoms from each sample were mounted on glass slides with Hyrax mounting medium. Five to six hundred frustules per slide were counted and identified by species (varieties and forms where possible) according to Hustedt (10) and Patrick and Reimer (11) under 1000x oil immersion lens of a microscope. The conventional criteria of frustule size, shape, and ornamentation were used to identify diatoms. Frustules were counted as one whether they were together or separated. The valve view was commonly used for identification purposes, but many girdle views were also identified and counted. Scanning three columns on each slide was done under 100x magnification to account for any diatoms missed in the first counts and their presence was indicated by a (+). In this way presence and relative abundance of nearly all diatom taxa epiphytic on pond bottom macrophytes was recorded. All diatom slides used in this study are at WQML in Durant, Oklahoma. RESULTS AND DISCUSSION Over 1000 diatoms/slide were present in complete and fragmented forms and oriented in valve views and girdle views. Frequently debris concealed a critical part of the diatom and prevented identification. Undoubtedly, I missed some taxa. The counts for each taxon represented only the relative abundance of each taxon in relation to each other on a 4-m length of macrophyte and were not absolute values. Table 2 contains the average abundance of taxa for the five samples in each pond. These numbers were converted to diversity indices to give an expression of the diatom community which was correlated with physicochemical parameters (12). I counted 20,883 diatoms representing 130 taxa in 25 genera in the 40 samples. The genus Navicula had the most species (thirty-seven) followed by Nitzschia (fifteen and Pinnularia (eleven). Fifty-seven taxa not previously reported for the state of Oklahoma were found. Achnanthes linearis and Cocconeis placentula were the most abundant species. In each pond A. linearis populations were larger in May than in August, especially May samples from the model ponds, which had at least three times as many diatoms as did the August samples. Populations of A. linearis in pond 1A did not change much and were lower than those at the other ponds. Cocconeis placentula also was more abundant in May than in August samples in the farm ponds; the reverse was true in the model ponds. There was nearly a twofold difference in populations for all the ponds between the May and August samples. In May these two codominant species, A. linearis and C. placentula, were represented by over 280 diatoms in the farm ponds and over 440 diatoms in the model ponds. In August samples the codominants together did not total 200 diatoms, except in pond 9, which had a combined total of 425 diatoms. In August other species seemed like codominants, including Epithemia zebra var. porcellus, which composed nearly half the diatoms in pond 8, and Navicula accomoda, which composed one-fourth of the diatoms in pond 15. In the August samples of pond 1A, Cocconeis placentula, Achnanthes linearis, Navicula cryptocephala, Nitzschia fonticola, and Synedra rumpens var. familiaris made up over 350 diatoms (Table 2). Other taxa, Achnanthes linearis f. curta, Nitzschia frustulum and Rhopalodia gibba, were found in relatively low numbers in all ponds on both dates. Some other diatoms, which were prevalent in just one pond in May and August, were Cocconeis placentula var. euglypta and Eunotia pectinalis var. minor f. impressa (pond 1A) and Navicula heufleri var. leptocephala and Nitzschia amphibia (pond 15). ACKNOWLEDGMENT This research was supported by USDA-Science and Education Administration, Fed-

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5 68 eral Research, Water Quality Management Laboratory, Durant, Oklahoma and University of Oklahoma, Department of Botany and Microbiology, Norman, Oklahoma REFERENCES 1. M. MALONEY, Proc. Okla. Acad. Sci. 24: (1944). 2. D. V. LEAKE, Am. Midl. Nat. 34: (1945). 3. A. R. KOCH and P. G. RISSER, Proc. Okla. Acad. Sci. 54: (1974). 4. A. R. KOCH, Proc. Okla. Acad. Sci. 55: (1975). 5. L. A. PFIESTER and S. TERRY, in press. 6. J. M. COOPER and J. WILHM, Southwest. Nat. 19: (1975). 7. J. WILHM, J. COOPER, and H. NAMMINGA, Hydrobiologia 57: (1978). 8. J. SEYFER and J. WILHM, Southwest. Natur. 22: (1977). 9. A. VAN DER WERFF, Int. Assoc. Theor. Appl. Limnol. 12: (1955). 10. F. HUSTEDT, "Bacillariophyta," in: A. PASCHER, Die Süsswasser-Flora Mitteleuropas, vol. 10, Jena, R. PATRICK and C. W. REIMER, The diatoms of the United States, Vol. 1, Monogr. No. 13, Acad. Nat. Sci. Philadelphia, W. TROEGER, in press.